NOPR Community:

Mechanochemical synthesis of nanohydroxyapatite bioceramics

2013-12-12T16:38:16Z

Title: Mechanochemical synthesis of nanohydroxyapatite bioceramics Authors: Adzila, Sharifah; Sopyan, Iis; Yong, Tan Chou; Singh, Ramesh; Hoong, Wong Yew; Purbolaksono, J; Hamdi, Mohd. Abstract: Nanosized hydroxyapatite powder has been synthesized by the mechanochemical method using a dry mixture of calcium hydroxide and diammonium hydrogen phosphate. The effect of mechanochemical process on powder properties has been investigated. Three rotation speeds of 170 rpm, 270 rpm and 370 rpm have been employed with 15 hours milling time. Characterization of the nanopowders has been accomplished by Fourier transform infra red, X-ray diffraction and transmission electron microscopy analyses. The samples have been prepared and sintered in air at varying temperatures ranging from 1050–1350 °C. Results show that increase in rotation speed (370 rpm) increases the crystallite size (9–21 nm). Agglomerate formation with irregular shapes is found in the samples prepared at 270 and 370 rpm. The sintering process influences the stability of powder by yielding TCP phase at all the sintering temperatures. At 370 rpm, the sample sintered at 1250 °C shows the maximum relative density of 95.3% as well as hardness of 5.3 GPa. Page(s): 1570-1575

Solvent-free synthesis of jasminaldehyde using double metal cyanide based solid acid catalysts

2013-12-12T16:38:09Z

Title: Solvent-free synthesis of jasminaldehyde using double metal cyanide based solid acid catalysts Authors: Patil, Mallikarjun V; Sharma, Sumeet K; Jasra, Raksh V Abstract: The catalytic activity of Fe-Zn double metal cyanide catalysts is studied for the solvent-free synthesis of jasminaldehyde by liquid phase condensation of benzaldehyde and 1-heptanal at 433 K. The highest conversion of 1-heptanal (93%) with 77% selectivity to jasminaldehyde is achieved under the optimum reaction conditions. The presence of co-ordinatively unsaturated Zn²⁺in the structural framework of Fe-Zn double metal cyanide assists the condensation reaction. The effects of complexing and co-complexing agent, amount of catalyst, benzaldehyde to 1-heptanal molar ratio and temperature on the selectivity of jasminaldehyde is reported. Page(s): 1564-1569

Facile synthesis of highly dispersed PtSn nanoparticles on carbon nanotubes with excellent ethanol electrooxidation performance

2013-12-19T16:38:46Z

Title: Facile synthesis of highly dispersed PtSn nanoparticles on carbon nanotubes with excellent ethanol electrooxidation performance Authors: Wu, Bohua; Gong, Ming; Chu, Jia; Wang, Xiaoqin; Xiong, Shanxin Abstract: Stable and uniform PtSn nanoparticles on the surface of carbon nanotubes with ultrafine particle sizes have been prepared via the ionic liquid polymer method. Morphology and electrochemical properties of the PtSn nanoparticles supported on the ionic liquid (IL) polymer-functionalized carbon nanotubes (PtSn/CNTs-f nanohybrids) have been investigated by transmission electron microscopy and cyclic voltammetry. The average diameter of PtSn nanoparticles in the PtSn/CNTs-f nanohybrids is 1.6±0.5 nm, which is much smaller than that deposited on pristine carbon nanotubes (PtSn/CNTs-p nanohybrids, 6±2 nm). The electrochemical active surface area (ESA) of the PtSn/CNTs-f nanohybrids is about twice as high as that of the PtSn/CNTs-p nanohybrids. In comparison to the PtSn/CNTs-p nanohybrids, PtSn/CNTs-f nanohybrids exhibit unexpectedly high activity and stability towards ethanol electrooxidation which may be attributed to the higher dispersion, smaller particle size and higher ESA of the PtSn nanoparticles on the IL polymer functionalized CNTs material. The results indicate that PtSn/CNTs-f nanohybrids are promising anodic electrocatalyst for direct ethanol fuel cells. Page(s): 1557-1563

Solvothermal synthesis and characterization of zinc sulphide nanoparticles

2013-12-23T16:39:28Z

Title: Solvothermal synthesis and characterization of zinc sulphide nanoparticles Authors: Mishra, Deepti; Prabhakar, Priyanka; Lahiri, Swati; Amritphale, S S; Chandra, Navin Abstract: Zinc sulphide nanoparticles have been synthesized by solvothermal approach involving refluxing of an aqueous solution of zinc acetate and sodium sulphide in presence of ethylene glycol and cetyl trimethyl ammonium bromide as surfactant. The nanoparticles have been characterized by X-ray diffraction, Fourier transform infrared spectroscopy, field emission scanning electron microscopy, energy-dispersive X-ray spectroscopy, differential scanning calorimetry, thermogravimetric analysis, ultraviolet-visible spectroscopy and transmission electron microscopy. The FESEM results indicate that the particles are almost spherical in shape with size varying in the range of 27.7–49.5 nm, whereas TEM micrograph indicates formation of particles of size in the range of 5–8 nm. EDX spectrum reveals the predominance of carbon, zinc, oxygen and sulphur. Page(s): 1591-1594